This invention relates to apparatus for curing ultraviolet (UV) coatings on filaments and the like which prevents the infrared (IR) radiation from overheating the UV curable coating and destroying the same by reflecting the infrared light and passing the ultraviolet light. This is done by providing a concentric tube about the main tube which reflects the IR light and permits the UV light to pass through to the outer tube and through the inner tube to the filament to cure the resin.
For purposes of understanding the background of the invention, reference is made to U.S. Pat. No. 4,710,638 issued Dec. 1, 1987, which is hereby incorporated by reference. This reference shows a prior art radiation lamp and reflectors for directing the radiation on a coated filament.
Optical fibers are very delicate and can be strengthened by applying and curing secondary and tertiary coatings. The fibers are coated with a UV curable resin and an UV irradiator cures the resins. Available UV irradiators generate a large amount of energy, typically 3000-6000 watts of energy, some of which is in the infrared range, which can be damaging to the coating. There is, therefore, a need for an irradiator that minimizes the amount of IR radiation that reaches the UV curable coating.
Overton, U.S. Pat. No. 5,092,264, shows a method of controlling the temperature at which the coating on an optical fiber is cured. Overton controls the control the temperature to obtain a coating material with predetermined moduli by means of IR absorbing gas which is moved between two concentric tubes.
It is an object of this invention to provide a simple and non-expensive method of controlling the IR radiation generated by a UV curing apparatus to avoid overheating of the coating of an optical filament or the like.
It is another object of this invention to provide a tubular apparatus having inner and outer tubes that permits the innertube to be removed for replacement or cleaning, if desired, due to the resin residue which builds up on the inside of the innertube over time, degrading its ability to transmit the UV radiation. This can be done without removal of the outertube which has a means for controlling the IR radiation.
It still another object of this invention is to provide a simple mirror reflective means which is an over jacket for the main tube through which the filament passes and which will transmits UV energy while minimizing the IR energy.
It is a further object of this invention is to provide a means for maintaining the mirrored tube in good condition without having to remove it frequently as it is necessary with the inner processing tube.
These and other objects of this invention will be apparent from the following description and drawings.
In summary, this invention provides a system for controlling the IR radiation while permitting transmittal of the UV radiation and which allows ready cleaning of the innertube without damage to the outertube.